The effects of adsorption and concentration on rates of protein degrad
ation by marine bacteria were examined by measuring hydrolysis and rem
ineralization of the radiolabeled protein, ribulose-1,5-bisphosphate c
arboxylase-oxygenase ([methyl-H-3]Rubisco). Protein adsorbed at low su
rface concentrations on glass beads had hydrolysis and remineralizatio
n rate constants 247% and 282% higher than protein bound at high surfa
ce concentrations. Moreover, thin films of bound protein were hydrolyz
ed and remineralized 522% and 1,033% faster than comparable pool sizes
of dissolved protein. At high concentrations, however, rates of hydro
lysis and remineralization were not significantly different between pr
oteins in dissolved or sorbed pools. Results demonstrate that proteins
adsorbed to surfaces can be as bioavailable as those in solution. In
fact, the sorption process may actually aid bacterial degradation by c
oncentrating the protein and hydrolysates at an interface and by unfol
ding proteins to relax steric hindrance and expose a higher proportion
of bonds to bacterial endo- and exohydrolases.